Postpartum depression (PPD) affects 10-15% of women ? and is associated with a range of severe negative outcomes that impact both the mother's and child's well-being. Even elevated depressive symptoms not meeting full MDD criteria have a debilitating effect on the mother and infant. Therefore, there is a critical opportunity and need to validate markers of risk during the prenatal period that could be used to guide early identification of the highest risk women; these markers might then be leveraged for prevention efforts and serve as targets of novel intervention strategies. Because women regularly access health care during pregnancy, this period presents an ideal opportunity to test and improve identification of risk. There is an emerging consensus that anhedonia ? insensitivity to reward ? is a core deficit in MDD. However, biological markers of anhedonia have not been studied in the perinatal period. The present proposal focuses on reward-related neural activity reflected in an event-related potential referred to as the reward positivity (RewP). The RewP is blunted among both adults and children with diagnosed MDD?and we have found that a reduced RewP prospectively predicts increases in depressive symptomatology and first onset of major depressive episodes?even when accounting for other known measures of risk. This proposal aims to extend our previous work to PPD?and test the novel hypothesis that a blunted RewP obtained during pregnancy will prospectively predict increased depressive symptoms and new depressive episodes in the postpartum period. We will record EEG during a reward task in 300 pregnant women in conjunction with prenatal care visits at an OB/GYN office between 16 and 32 weeks gestation. Depressive symptoms and disorders will be assessed both at baseline and six weeks following delivery?so that the predictive ability of the RewP can be examined when controlling for other known risk factors (e.g., history of MDD and baseline symptoms). This sample size was chosen to assure adequate variability in postpartum depressive outcomes and sufficient cases of PPD. Aim 1 is to examine the relationship between the RewP and current depressive symptoms and diagnoses at 16 weeks gestation. Aim 2 assesses whether a smaller RewP at baseline will prospectively predict increases in depression during the postpartum period. Aim 3 will determine whether blunted reward-related neural activity (i.e., the RewP) during pregnancy predicts depressive outcomes even after controlling for other baseline predictors of postpartum depression. We will also examine time-frequency based measures of reward (i.e., reward-related delta band activity), and examine positive and negative predictive value of reward-related neural activity in predicting depressive outcomes in the postpartum period?both alone and in conjunction with baseline risk factors. This R21 will provide the first evidence that hypoactive reward-related neural activity, assessed using EEG during pregnancy at a routine OB/GYN visit, could be used to improve the prediction of increased depression during the postpartum period.